In most diesel engine systems there is a filter device through which fuel must flow to reach the engine. When the engine apparatus is subjected to temperatures in the region of zero degrees Fahrenheit and lower, there is a tendency for crystals and solid wax particles to form in the diesel fuel. Such conditions cause clogging of the fuel filter device.
In a conventional diesel engine apparatus only a portion of the fuel pumped to the engine is used, and the excess fuel which flows from the engine contains gas, in the form of entrained air, which is ordinarily vented from the fuel in the fuel tank as the excess fuel with the entrained air therein returns to the fuel tank.
Attempts have been made to mix heated return fuel with fuel flowing from the fuel tank in order to provide fuel to the engine at a temperature which does not permit the formation of wax particles in the fuel, to avoid clogging of the fuel filter. However, the entrained air in the heated return fuel presents a problem, due to the fact that the diesel engine must have sufficient fuel to operate, and excessive air in the fuel robs the engine of fuel necessary for operation.
Various methods have been employed in an attempt to overcome these problems. For example, No. 1 fuel oil is mixed with the conventional No. 2 diesel fuel oil, to provide a fuel in which wax crystallization does not occur so readily in cold weather. This mixing process has not been found to be satisfactory and adds to the expense of the fuel.
U.S. Pat. Nos. 2,881,828 and 3,472,214 show the use of heat exchanger devices to heat the fuel, to avoid wax crystallization. However, such devices may not provide heat to the fuel until a significant period of time has elapsed, and therefore fuel filter clogging may occur with initial operation.
U.S. Pat. No. 3,768,454 shows the use of a fuel tank which has a mixing zone with a temperature responsive valve controlling flow of fuel with respect to the mixing zone. Such a system requires an objectionable special fuel tank.
U.S. Pat. No. 2,599,699 recognizes the problem involved as entrained air flows from the diesel engine with the excess heated fuel. This patent shows a device which attempts to eliminate the air from the heated return fuel prior to mixing of the heated fuel with fuel flowing from the fuel tank. However, the device of this patent employs a fuel return tank which occupies excessive space and which employs baffles to separate air from the heated fuel. This device is therefore not satisfactory for use in the diesel engine system.
It is therefore an object of this invention to provide diesel fuel control apparatus and a system which supplies conventional diesel fuel to a diesel engine at a proper temperature and without wax crystallization therein when the diesel engine apparatus is exposed to low temperatures.
It is another object of this invention to provide such diesel fuel control apparatus which also supplies fuel to a diesel engine at a proper temperature at all environmental temperatures.
It is another object of this invention to provide such diesel fuel control apparatus and a system in which the temperature of the fuel flowing to the diesel engine is sensed by a fuel temperature control device immediately following flow of the diesel fuel through a fuel filter unit, and the temperature control device controls the temperature of fuel flowing to the fuel filter unit. Thus, the temperature of the diesel fuel flowing into the fuel filter is always at a proper temperature for fuel flow through the fuel filter without wax crystallization in the fuel.
It is another object of this invention to provide such diesel fuel control apparatus and a system which does not require a special fuel tank.
It is another object of this invention to provide such a diesel engine fuel control apparatus and a system which does not employ a fuel heater device.
It is another object of this invention to provide such a diesel fuel control apparatus and system in which additional fuel conduit lines are not required in the installation thereof.
It is another object of this invention to provide such diesel fuel control apparatus and a system which can be easily and readily installed in an existing diesel engine apparatus and system.
It is another object of this invention to provide such diesel engine fuel control apparatus and a system which is relatively small in physical size.
It is another object of this invention to provide such diesel engine fuel control apparatus and a system by which air entrained in the heated return fuel is automatically removed from the mixture of heated return fuel and air during flow of the mixture for mixing of the heated return fuel with diesel fuel flowing from the fuel tank.
It is another object of this invention to provide such diesel fuel control apparatus and a system which can be a fixed original part of a diesel engine unit and in combination with a diesel fuel filter unit.
Other objects and advantages of the diesel fuel control apparatus and system of this invention reside in the construction and arrangement of parts, the combination thereof, the method of production, and the mode of operation, as will become more apparent from the following description.